Roof Framing Geometry

The tangent of 22 5 41421 laying out an octagon using a framing square we would take 12 on the blade and the number to be taken on the tongue is 12 41421 which is 4 97 or nearly 5.

Roof framing geometry.

However it has over 1 000 geometric roof framing drawings in the book as well for carpenters that are not comfortable using trigonometry. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape. Information gained by means of observation experience or experiment. It will take more than just reading to understand roof framing geometry.

With overhang selected drag slider to increment decrement birdsmouth seat width to suit. One half of 45 is 22 5. Roof framing geometry trigonometry for polygons polygons in mathematical context polygons in carpenters mathematical context central angle pi 2 n working angle pi 2 n 2 plan angle pi central angle 2 exterior angle plan angle 2 s is the length of any side of the polygon n is the number of sides. Gambrel roof framing geometry calculator metric this gambrel roof confines to a semicircle and starts as the top half of an equal sided octagon.

The pitch or steepness of a roof is often referred to in terms of the amount of vertical rise over a 12 horizontal run. Roof framing geometry is empirical type knowledge. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth. For example a 5 12 pitch roof will rise vertically 5 for every 12 it goes back horizontally.

There are smartphone apps available which can be used to sight a roof s pitch from the ground. You ll need to draw out the roof framing geometry.